IT’S 8:30 a.m. and Jim Ryan, the centerpiece of “Good Day New York,” is smashing a liquor bottle over the head of weatherman Dave Price – on live TV.

The bottle, one of those easy-break props used in bar-fight scenes in westerns, shatters into a thousand pieces that rain down on a stoic Price and scatter across the anchor desk.

This bit of manic slapstick leaves the show’s crew in tears, laughing – and is emblematic of the loose, unscripted banter that has turned the morning show into a ratings winner.

“Jim! You scratched the desk!” scolds Gail Yancosek, the show’s executive producer, during a commercial break. “Roland is not gonna be happy,” she jokes, referring to “10 O’Clock News” anchor John Roland.

But after “Good Day” finished second only to NBC’s “Today” show in last May’s all-important ratings sweeps, the “little morning show that could” it seems to be making a lot of folks happy – especially the ones in upstairs offices at WNYW/Ch. 5, (a division of News Corp. which also owns The Post).

“We’re the young upstarts that are going against the big guys,” Ryan says. “They’ll get the secretary of state to pontificate on the issues of the world stage, and we get the guy who’s responsible for keeping his teeth clean.”

In the early ’90s, “GDNY” was actually the most-watched local morning show in town – beating the three networks hands-down. But the show fell on hard times in the ratings, slipping to No. 3 and sometimes even No. 4.

In the last two years, “GDNY” has made an unsual comeback – possibly thanks, in part, to the station’s decision to promote the show with a barrage of spots (a new one every day) in primetime. The spots emphasized the show’s light touch and the good chemistry between its anchors. Ryan, meanwhile, was able to hang on through thin times and thick.

Ryan is something of a father figure around New York media circles for his bottomless boosterism to his Irish heritage and his work with the Inner Circle, the annual political lampoon staged by city reporters.

“He’s really smart and has this fabulous singing voice,” says an Inner Circle member. “He’s incredible at writing lyrics. I don’t know if you understand how hard that is, but he’s really good at it.”

Writing has always been Ryan’s specialty.

The 44-year news veteran, who started his career at age 17 as a copy boy for the Associated Press, spent six years at the Daily News as both a general assignment and investigative reporter.

He slipped into TV in 1974, landing a job as executive editor of news at WNBC/Ch. 4 and was later named its executive producer.

Ryan joined Fox 5/WNYW in 1985 as political reporter for “The 10 O’Clock News” He took over as anchor on “GDNY,” when the crack-of-dawn morning show launched in 1988.

“I detest getting out of bed,” he grumbles, complaining about his 4:30 a.m. wake-up and subsequent journey across town from his home on the Upper West Side to Channel 5 on E. 67th Street.

“The worst part of my day is from the sheets to the shower. Once I hit the shower I’m all right.”

Yancosek says much of the morning show’s strength lies in the chemistry between Ryan, Price and news-reader Lyn Brown, who usually ends up playing it straight against the pair’s improvised banter.

“Jim’s one of the greatest, smartest people I’ve ever worked with,” says Price after “GDNY” wraps for the day.